Does the iddah begin immediately after divorce if a man divorces his wife during a period of purity in which he had intercourse with her?

Scholars have differed regarding the occurrence of divorce if it takes place during a period of purity (tuhr) in which the husband had intercourse with his wife. The preponderant opinion is that it occurs, though it is forbidden. Then, they differed regarding theation of the waiting period (iddah) for a divorced woman who menstruates, whether it is by menstruation or by aqra' (periods of purity). The correct view is that it is calculated by menstruation. The iddah begins immediately upon the occurrence of the divorce and ends with the completion of three menstrual periods, unless it becomes apparent that she is pregnant, in which case her iddah ends with childbirth, by consensus.